I still have the hissing noise after I changed my brake booster and brake hose, and also did the front pads and rotors. The brakes so stop much better, but when I press on the brake I still have the hiss sound. any ideas? normal on a s-types? BTW I also did a brake flush last week as well! thanks again guys...

 

Is the hiss constant while your foot is on the pedal, or just a second or two as the brakes are being applied? If it's the latter, I'd say 'normal', and that you've got excellent hearing.

 

its just a quick second or 2. it does not hiss while the brake is pressed down, only while I am pressing it.

 

U may have a brake booster problem. Does the tach wander when pressing on the brake pedal?

 

Why would the tach wander?

 

Brother, that "Hiss" isn't from a Black Mamba... it may be a leak. Vaccume leaks can periodically make the tach wander as the ECU tries to richen up the lean condition. If the leak is only produced during depressing the brake pedal, the ECU may not throw a CEL due to vaccume quickly building up following each pedal depression.